Day 9: Enums & Option

Enums define a type by enumerating its possible values. Combined with pattern matching, they're incredibly powerful!

Defining Enums

enum Direction {
    North,
    South,
    East,
    West,
}

enum Message {
    Quit,                       // no data
    Move { x: i32, y: i32 },   // named fields
    Write(String),              // single value
    Color(u8, u8, u8),         // multiple values
}

The Option Enum

Rust has no null! Instead, it uses Option<T>:

enum Option<T> {
    Some(T),
    None,
}

Unlike null in other languages, you MUST handle both cases with Option. The compiler enforces this!

Pattern Matching with match

fn handle_option(opt: Option<i32>) {
    match opt {
        Some(value) => println!("Got: {}", value),
        None => println!("Nothing"),
    }
}

The Task

Implement safe_divide(a, b) that:

Returns None if b is 0
Returns Some(a / b) otherwise

Requirements

Return type is Option<i32>
Handle division by zero gracefully
safe_divide(10, 2) → Some(5)
safe_divide(10, 0) → None

Hints

fn safe_divide(a: i32, b: i32) -> Option<i32> {
    if b == 0 {
        None
    } else {
        Some(a / b)
    }
}